1. Field of the Invention
This invention relates to aerosol dispensing devices. In particular, it relates to aerosol dispensing devices which are able to dispense a spray without the use of a pre-dosed propellant gas.
2. The Related Art
Dispensing devices are known which can be fitted to aerosol dispensing containers, and can be used to dispense as an aerosol the contents of the container without the use of a predosed propellant gas, such as hydrocarbons, chlorofluorocarbons, dimethyl ether, or compressed gasses. Instead, the container is adapted to allow the user to introduce into the container atmospheric air to generate a positive pressure therein, which may in turn be used to dispense the aerosol in conventional fashion. Such systems may conveniently be called "user pressurised" dispensers.
For example, in GB 1 582 556 (Airspray), there is described an aerosol dispensing system which has a conventional type dispensing nozzle located on top of a one way valve, the system being a single self-contained unit which may be attached to a liquid filled container by a screw threaded collar. Co-axial with the nozzle is a circular channel of "U" shaped cross section which can accommodate a hollow piston, which on moving the piston up and down causes air to be introduced past a one way valve and into the container.
A further development of this aerosol dispensing system can be found in EP 238 611 (Airspray). This application describes a system similar to that above, but in which it is possible for air to be introduced into the fluid stream just prior to arriving at the spray button, thus providing what is perceived to be a drier spray in use.
However, these known systems have several disadvantages. Firstly, they tend to have their pumping and dispensing mechanisms located together at the same end of the container. In the case of the Airspray systems described above, the pumping and dispensing mechanisms are located coaxially, and therefore part of the pumping mechanism has to be removed from the container before the spraying mechanism can be accessed. This therefore precludes a smooth transition in use between the pumping and spraying actions, and also acts to prevent one handed use of the container by the user.
Additionally, because of the nature of the system, it has been found that a relatively large force is required by the user to generate a positive pressure in the container. The constraints of the system prevent the fitting to the system of a mechanical system which could lower the force, or at least the perceived force, required by the user to operate the system.
An additional disadvantage of such systems is that it has been found that users of such products are often reluctant to purchase refills for such systems. This may be because the refill pack, when sold, is typically much smaller than the container in which the fluid to be dispensed is stored. This in turn is because the fluid storage part of the dispensing container must not be full in use, but must provide a headspace for the dispensing unit to function effectively. This therefore means that the user must manually decant the fluid into the original fluid container, or alternatively the refill liquid can be sold to the consumer in a partly full container, which is the same size as the original. Neither situation is optimum for the user.
A further disadvantage of the Airspray systems described above is that they require a relatively large pressure, typically 2-3 bar, to be introduced into the container, and this must be introduced via a valve which is located adjacent the spraying means. This large pressure is the valve opening force, and is in part due to the fact that the device requires a relatively large headspace to operate, as described above.
The constraints this puts on the overall design of the container have meant that in use the user has to deliver a quite significant force to the container in a manner which, from an ergonomic viewpoint, is not particularly efficient, in order to generate the necessary internal pressure for aerosol dispensing. This pressurising motion is not a particularly convenient operation for the user to deliver, and usually requires two-handed operation of the device.
Many of the disadvantages of these known user pressurized systems, for example those described above, are disadvantages which are inherent from the type and configuration of the pressurization unit, particularly the pressurization unit described in the Airspray patent applications. In particular, these problems arise because of the constraints on pack design imposed by having the aerosol dispensing nozzle and air inlet valves collocated in the same area of the device. The problem is particularly acute with the Airspray pressurization units, because the dispensing nozzle and air inlet configuration are coaxial.
The problem is also made worse because the design of the Airspray pressurization unit requires in practice that the whole volume of the aerosol container, which is typically fairly large, be raised to an elevated pressure in use. This in turn provides important and costly restraints on the design and manufacture of the aerosol apparatus.
It is an object of the invention to provide a user-pressurised device which has improved ease and simplicity of use for the user, in terms of the ease of pressurization of the device, ease of dispensing of the aerosol, and ease of refillability.
It is a further object of the invention to provide a user pressurised aerosol device which facilitates single handed pressurisation and use by the user, preferably in a simultaneous, or at least rapidly sequential fashion.
It is a further object of the invention to provide a user pressurised aerosol device which has increased ease of use by the user, due to the decreased force, or at least perceived force required by the user in order to generate the internal pressure required for dispensing.
It is a further objective of the invention to provide a user pressurised aerosol dispensing device which may have a reduced size compared to conventional user pressurised devices.
The device according to the invention may conveniently improve on other disadvantages suffered by the prior art.